This invention relates generally to a method for producing a polyethylene oxide implant and, in particular, to a method for producing a biocompatible crosslinked polyethylene oxide gel which can be injected into the human body for tissue replacement and augmentation.
It is well known that hydrogels have been used in many biomedical applications, as they can be made non-toxic and compatible with tissue. U.S. Pat. Nos. 4,983,181 and 4,994,081, which issued in 1991 to Civerchia, teach a method of polymerizing a hydrogel in the presence of a crosslinking agent to form a three dimensional polymeric meshwork having controlled spacings between the molecules thereof to anchor the macromolecules which have a known size and to insure that the micromolecules will be substantially uniformly interspersed within the polymeric meshwork of the polymerized hydrophilic monomer. The step of forming the crosslinking of the hydrogel can be performed with a crosslinking agent which may be external, such as ultraviolet radiation, or a crosslinking agent added to the hydrogel clear viscous monomer solution, which crosslinking agent may be, for example, ethyleneglycol dimethacrylate. The hydrogel taught in these patents is a transparent collagen hydrogel which is capable of promoting epithelial cell growth.
Some of the drawbacks of using collagen gels are that they typically biodegrade in three to six months, and are well known for their infectious and immunologic reactions. In addition, collagen implants are, in time, colonized by the recipient cells and vessels.
Another type of substance commonly used in biomedical applications is a silicone gel. However, silicone gels are also known to cause immunologic reactions, and tend to migrate away from the implantation site. In addition, silicone implants become encapsulated by dense fibrous tissues created by cellular reactions to a foreign substance implanted into the tissue. Finally, while silicone gels do allow for efficient oxygen diffusion, there is insufficient transportation of nutrients across the space that the implants occupy.